Scroll compressor

ABSTRACT

To prevent or reduce functional disturbance of a back-pressure control valve caused by contamination, a scroll compressor includes: a scroll unit having a fixed scroll and an orbiting scroll; a discharge chamber (H3) into which fluid compressed by the scroll unit is discharged; a back-pressure chamber (H4) configured to apply a back pressure that presses the orbiting scroll against the fixed scroll; and a switching valve (900) disposed at some midpoint of a back-pressure supply passage (L1) connecting the discharge chamber (H3) and the back-pressure chamber (H4) in communication. The switching valve (900) is configured to switch between a first state in which the switching valve (900) connects the discharge chamber (H3) with the back-pressure chamber (H4) in communication and a second state in which the switching valve (900) connects the back-pressure chamber (H4) with a suction chamber (H1), in accordance with an operational state of the scroll unit.

TECHNICAL FIELD

The present invention relates to a scroll compressor that compresses fluid such as a gas refrigerant.

BACKGROUND ART

A scroll compressor includes a scroll unit having a fixed scroll and an orbiting scroll engaged with each other. In the scroll unit, the orbiting scroll orbits about the axis of the fixed scroll to change the volume of the compression chamber defined by the fixed scroll and the orbiting scroll. Thereby, the scroll unit compresses the gas refrigerant and discharges the compressed gas refrigerant. In the scroll compressor, a back pressure is applied to the back surface of the orbiting scroll to press it against the fixed scroll so as to prevent or reduce the separation of the orbiting scroll from the fixed scroll during the compression operation, thereby minimizing the probability of compression failure. In this event, as described in JP 2012-207606 A (Patent Document 1), the back pressure applied to the back surface of the orbiting scroll is adjusted using a back-pressure control valve disposed in a communication passage connecting the back-pressure chamber and the suction chamber in communication.

REFERENCE DOCUMENT LIST Patent Document

Patent Document 1: JP 2012-207606 A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In the back-pressure chamber, if contamination (foreign matter) is caused by, for example, abrasion of sliding portions, the contamination is introduced into the back-pressure control valve. When contamination is introduced into the back-pressure control valve, the contamination may, for example, clog a filter contained in the back-pressure control valve, and may disturb the functionality of the back-pressure control valve. As a result, the back-pressure control valve may become unable to properly adjust the back pressure.

Therefore, an object of the present invention is to provide a scroll compressor in which functional disturbance of the back-pressure control valve caused by contamination can be reduced or prevented.

Means for Solving the Problems

To this end, the scroll compressor according to the present invention includes: a scroll unit having a fixed scroll and an orbiting scroll; a discharge chamber into which fluid compressed by the scroll unit is discharged; a back-pressure chamber configured to apply a back pressure that presses the orbiting scroll against the fixed scroll; and a switching valve disposed at some midpoint of a communication passage connecting the discharge chamber and the back-pressure chamber in communication. The switching valve is configured to switch between a first state in which the switching valve connects the discharge chamber with the back-pressure chamber in communication and a second state in which the switching valve connects the back-pressure chamber with a space external to the back-pressure chamber in communication, in accordance with an operational state of the scroll unit.

Effects of the Invention

According to the present invention, functional disturbance of the back-pressure control valve caused by contamination can be reduced or prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view of an example of a scroll compressor.

FIG. 2 is a block diagram for illustrating the flows of gas refrigerant and lubricating oil.

FIG. 3 is a cross-sectional view of a substantial part of a switching valve according to a first embodiment when the scroll compressor is in operation.

FIG. 4 is a cross-sectional view of the substantial part of the switching valve according to the first embodiment when the scroll compressor is not in operation.

FIG. 5 is a cross-sectional view of a substantial part of a switching valve according to a second embodiment when the scroll compressor is in operation.

FIG. 6 is a cross-sectional view of the substantial part of the switching valve according to the second embodiment when the scroll compressor is not in operation.

FIG. 7 is a cross-sectional view of a substantial part of a switching valve according to a third embodiment when the scroll compressor is in operation.

FIG. 8 is a cross-sectional view of the substantial part of the switching valve according to the third embodiment when the scroll compressor is not in operation.

FIG. 9 is a cross-sectional view of a substantial part of a switching valve according to a modification of the first embodiment.

FIG. 10 is a cross-sectional view of a substantial part of a switching valve according to a modification of the second embodiment.

MODES FOR CARRYING OUT THE INVENTION

Embodiments for implementing the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an example of a scroll compressor.

A scroll compressor 100 is incorporated, for example, in a refrigerant circuit (external device) of a vehicle air conditioner. The scroll compressor 100 compresses a gas refrigerant (fluid) drawn from the low-pressure side of the refrigerant circuit and then discharges the compressed gas refrigerant. The scroll compressor 100 includes a housing 200, a scroll unit 300 for compressing a low-pressure gas refrigerant, an electric motor 400 for driving the scroll unit 300, an inverter 500 for controlling the electric motor 400, and a support member 600 rotatably supporting one end of a drive shaft 420 of the electric motor 400. Examples of the refrigerant in the refrigerant circuit may include a CO₂ (carbon dioxide) refrigerant. Note that although the scroll compressor 100 is described as an inverter-integrated compressor herein, this is merely an illustrative example. Alternatively, the scroll compressor 100 may be separated from the inverter.

The housing 200 includes a front housing 220, a rear housing 240, and an inverter cover 260. The front housing 220 houses the scroll unit 300, the electric motor 400, the inverter 500, and the support member 600. The rear housing 240 is fastened to one end of the front housing 220. The inverter cover 260 is fastened to the other end of the front housing 220. The front housing 220, the rear housing 240, and the inverter cover 260 are integrally fastened by a plurality of fasteners 700 including, for example, bolts and washers, so as to constitute the housing 200 of the scroll compressor 100.

The front housing 220 is configured to include a cylindrical peripheral wall portion 222 and a disk-shaped partition wall portion 224 that divides the internal space surrounded by the peripheral wall portion 222 into two in the axial direction. As used herein, the term “cylindrical” refers to a substantially and seemingly cylindrical shape. Thus, any cylindrical shape herein may have, for example, one or more ribs for reinforcement and bosses for attachment, etc. in the outer peripheral surface (the same also applies to other shape-related terms below). The internal space of the front housing 220 is divided by the partition wall portion 224 into a first space 220A for housing the scroll unit 300, the electric motor 400, and the support member 600, and a second space 220B for housing the inverter 500.

The opening at the one end of the peripheral wall portion 222 is closed by the disk-shaped rear housing 240. The opening at the other end of the peripheral wall portion 222 is closed by the inverter cover 260. At a center portion of one surface of the partition wall portion 224, a cylindrical support portion 224A is formed extending from the partition wall portion 224 toward the one end of the peripheral wall portion 222. The other end of the drive shaft 420 of the electric motor 400 is rotatably supported by the support portion 224A via a bearing 720 press-fitted onto the inner peripheral surface of the support portion 224A.

In addition, a suction port P1 for drawing in gas refrigerant is formed in the peripheral wall portion 222. The gas refrigerant from the low-pressure side of the refrigerant circuit is drawn into the first space 220A of the front housing 220 through the suction port P1. Accordingly, the first space 220A of the front housing 220 functions as a suction chamber H1 for drawing in gas refrigerant. In the suction chamber H1, the gas refrigerant flows around the electric motor 400, thereby cooling the electric motor 400. In the first space 220A, spaces on axially opposite sides of the electric motor 400 communicate with each other so as to constitute the single suction chamber H1. In the suction chamber H1, the gas refrigerant flows in the form of a mixed fluid containing a small amount of lubricating oil.

The rear housing 240 is fastened by the plurality of fasteners 700 to an opening at the one end of the peripheral wall portion 222 of the front housing 220. The rear housing 240 closes the opening at the one end of the front housing 220. The rear housing 240 also has a discharge port P2 for discharging the gas refrigerant compressed by the scroll unit 300 to the high-pressure side of the refrigerant circuit. In addition, an oil separator 740 is incorporated in the rear housing 240. The oil separator 740 is configured to separate lubricating oil from the gas refrigerant compressed by the scroll unit 300. The gas refrigerant from which the lubricating oil has been separated by the oil separator 740 (although not necessarily completely; a small amount of lubricating oil may be left in such gas refrigerant) is discharged to the high-pressure side of the refrigerant circuit through the discharge port P2. Meanwhile, the lubricating oil separated by the oil separator 740 is introduced to a back-pressure supply passage L1, which will be described in detail later.

The scroll unit 300 is housed in a portion, closer to the one end, of the front housing 220. Specifically, the scroll unit 300 includes a fixed scroll 320 fixed to one surface of the rear housing 240, and an orbiting scroll 340 disposed on a side, opposite to the rear housing 240, of the fixed scroll 320.

The fixed scroll 320 includes a disk-shaped bottom plate 322 fixed to one surface of the rear housing 240, and an involute curve-shaped wrap (spiral blade) 324 extending from one surface of the bottom plate 322 to the orbiting scroll 340. The orbiting scroll 340 includes a disk-shaped bottom plate 342 disposed facing the bottom plate 322 of the fixed scroll 320, and an involute curve-shaped wrap 344 extending from one surface of the bottom plate 342 to the fixed scroll 320.

The fixed scroll 320 and the orbiting scroll 340 are engaged with each other so that the circumferential angles of the wraps 324 and 344 are offset from each other and the sidewalls of the wraps 324 and 344 are partially in contact with each other. Accordingly, in the scroll unit 300, a crescent-shaped closed space, that is, a compression chamber H2 for compressing the gas refrigerant, is defined between the fixed scroll 320 and the orbiting scroll 340.

At a center portion of the bottom plate 322 of the fixed scroll 320, a discharge passage L2 for discharging the gas refrigerant compressed by the compression chamber H2 is formed. In a center portion of the other surface of the bottom plate 322, a discharge chamber H3 for temporarily storing the gas refrigerant discharged from the compression chamber H2 through the discharge passage L2 is formed. The discharge chamber H3 is formed of a columnar recess. In addition, a one-way valve 326 is attached to the other surface of the bottom plate 322. The one-way valve 326 is formed of, for example, a reed valve, and configured to permit the flow of the gas refrigerant from the compression chamber H2 to the discharge chamber H3 and block the flow of the gas refrigerant from the discharge chamber H3 to the compression chamber H2.

The electric motor 400 is, for example, a three-phase alternating current motor, and includes the drive shaft 420, a rotor 440, and a stator core unit 460 disposed radially outside the rotor 440. The stator core unit 460 of the electric motor 400 is supplied with an alternating current to which a direct current from, for example, an in-vehicle battery (not shown) is converted by the inverter 500.

The drive shaft 420 is connected to the orbiting scroll 340 via a crank mechanism, which will be described later, and transmits the rotational driving force of the electric motor 400 to the orbiting scroll 340. One end, which is closer to the orbiting scroll 340, of the drive shaft 420 passes through a through hole 600A formed in the support member 600 and is rotatably supported on a bearing 760 fixed to the support member 600. The other end of the drive shaft 420 is rotatably supported on the bearing 720 press-fitted into the support portion 224A of the front housing 220, as described above.

The rotor 440 is disposed radially inside the stator core unit 460 and rotatably supported on the drive shaft 420 that is fitted (e.g., press-fitted) into a shaft hole formed at the radial center of the rotor 440. When a current is supplied to the electric motor 400 from the inverter 500, a magnetic field is generated in the stator core unit 460 and a torque acts on the rotor 440 to rotationally drive the drive shaft 420.

The support member 600 has a bottomed cylindrical shape having the same outer diameter as the bottom plate 322 of the fixed scroll 320. The inner peripheral surface of the support member 600 has a stepped columnar shape with two inner diameters, the larger of which is closer to the opening and the smaller of which is closer to the bottom. The orbiting scroll 340 of the scroll unit 300 is housed in the space defined by the larger diameter portion of the inner peripheral surface of the support member 600. The surface at the open end of the support member 600 is fastened to the one surface of the bottom plate 322 of the fixed scroll 320 with, for example, a fastener (not shown). Thus, the opening of the support member 600 is closed by the fixed scroll 320 so that a back-pressure chamber H4 for pressing the orbiting scroll 340 against the fixed scroll 320 is defined.

The bearing 760 is fitted on the smaller diameter portion of the inner peripheral surface of the support member 600. The one end of the drive shaft 420 of the electric motor 400 is rotatably supported on the bearing 760. The through hole 600A is formed at a radially center portion of the bottom wall located at the deepest position of the support member 600. The one end of the drive shaft 420 passes through the through hole 600A. A sealing member 780 is disposed between the bearing 760 and the bottom wall to ensure the airtightness of the back-pressure chamber H4.

In the space defined by the larger diameter portion of the inner peripheral surface of the support member 600, an annular thrust plate 800 is disposed between the bottom plate 342 of the orbiting scroll 340 and the step portion at which the smaller diameter portion and the larger diameter portion meet with each other. The step portion of the support member 600 receives a thrust force from the orbiting scroll 340 via the thrust plate 800. Sealing members 820 for ensuring the airtightness of the back-pressure chamber H4 are disposed at the step portion of the support member 600 and at a portion, in contact with the thrust plate 800, of the bottom plate 342 of the orbiting scroll 340.

The back-pressure supply passage L1 is formed to extend through the rear housing 240, the fixed scroll 320, and the support member 600. Through the back-pressure supply passage L1, the lubricating oil separated by the oil separator 740 that is incorporated in the rear housing 240 is supplied to the back-pressure chamber H4 that is defined by the support member 600. The lubricating oil supplied from the oil separator 740 to the back-pressure chamber H4 is used as a back pressure that presses the orbiting scroll 340 against the fixed scroll 320. An orifice 840 for limiting the flow rate of the lubricating oil is disposed at some midpoint of the back-pressure supply passage L1. The back-pressure supply passage L1 is an example of a communication passage connecting the discharge chamber H3 and the back-pressure chamber H4 in communication.

A back-pressure control valve 860 is attached to the smaller inner diameter portion of the support member 600. The back-pressure control valve 860 operates in accordance with the back pressure Pm in the back-pressure chamber H4 and the suction pressure Ps in the suction chamber H1 so as to adjust the back pressure Pm in the back-pressure chamber H4 accordingly. Specifically, when the back pressure Pm in the back-pressure chamber H4 rises above a target pressure, the back-pressure control valve 860 opens and discharges the lubricating oil in the back-pressure chamber H4 to the suction chamber H1. As a result, the back pressure Pm in the back-pressure chamber H4 decreases. On the other hand, when the back pressure Pm in the back-pressure chamber H4 falls below the target pressure, the back-pressure control valve 860 closes and stops discharging the lubricating oil from the back-pressure chamber H4 to the suction chamber H1. As a result, the back pressure Pm in the back-pressure chamber H4 increases. In this way, the back-pressure control valve 860 adjusts the back pressure Pm in the back-pressure chamber H4 to the target pressure.

A refrigerant introduction passage L3 is defined between the inner peripheral surface of the peripheral wall portion 222 of the front housing 220 and the outer peripheral surface of the support member 600. The refrigerant introduction passage L3 connects the suction chamber H1 and a space H5 located in an outer peripheral portion of the scroll unit 300 in communication. Through the refrigerant introduction passage L3, the gas refrigerant is introduced from the suction chamber H1 to the space H5. Thus, the pressure in the space H5 is equal to the pressure in the suction chamber H1.

The crank mechanism has a cylindrical boss portion 880, a crank pin 882, an eccentric bushing 884, and a slide bearing 886. The boss portion 880 is formed protruding from the other surface of the bottom plate 342 of the orbiting scroll 340. The crank pin 882 is eccentrically erected on the one end surface of the drive shaft 420. The eccentric bushing 884 is eccentrically mounted to the crank pin 882. The slide bearing 886 is fitted into the boss portion 880. The eccentric bushing 884 is supported by the boss portion 880 via the slide bearing 886 so as to be rotatable relative to the boss portion 880. At the one end of the drive shaft 420, a balancer weight 888 for balancing the centrifugal force of the orbiting scroll 340 is attached. In addition, although not shown, an anti-rotation mechanism that prevents the rotation of the orbiting scroll 340 is also provided. Accordingly, the orbiting scroll 340 is orbitable about the axis of the fixed scroll 320 via the crank mechanism in a state in which the rotation of the orbiting scroll 340 is prevented.

FIG. 2 is a block diagram for illustrating the flows of gas refrigerant and lubricating oil.

The gas refrigerant from the low-pressure side of the refrigerant circuit is introduced into the suction chamber H1 through the suction port P1, and it is then introduced into the space H5 located in the outer peripheral portion of the scroll unit 300 through the refrigerant introduction passage L3. After being introduced into the space H5, the gas refrigerant is then taken into the compression chamber H2 of the scroll unit 300, and compressed as the volume of the compression chamber H2 changes. After being compressed in the compression chamber H2, the gas refrigerant is discharged into the discharge chamber H3 through the discharge passage L2 and the one-way valve 326, and it is then introduced into the oil separator 740. The gas refrigerant from which the lubricating oil has been separated by the oil separator 740 is discharged to the high-pressure side of the refrigerant circuit through the discharge port P2. Meanwhile, the lubricating oil separated by the oil separator 740 is supplied to the back-pressure chamber H4 through the back-pressure supply passage L1 at a flow rate restricted by the orifice 840. After being supplied to the back-pressure chamber H4, the lubricating oil is discharged into the suction chamber H1 via the back-pressure control valve 860.

The lubricating oil supplied to the back-pressure chamber H4 is used as a back pressure that presses the orbiting scroll 340 against the fixed scroll 320 as well as to lubricate sliding portions in the back-pressure chamber H4 and the like. Thus, contamination caused by, for example, abrasion of such sliding portions may be mixed in the lubricating oil present in the back-pressure chamber H4. If contamination mixes in the lubricating oil, the contamination may clog the filter contained in the back-pressure control valve 860 for adjusting the back pressure Pm in the back-pressure chamber H4. This may disturb the functionality of the back-pressure control valve 860, and the back-pressure control valve 860 may become unable to properly adjust the back pressure.

To address the above, a switching valve 900 is disposed at some midpoint of a portion, downstream of the orifice 840, of the back-pressure supply passage L1. The switching valve 900 is configured to discharge the lubricating oil in the back-pressure chamber H4 into the suction chamber H1 when the scroll unit 300 of the scroll compressor 100 stops its operation. Specifically, the switching valve 900 autonomously switches between a first state and a second state in accordance with the suction pressure Ps in the suction chamber H1, the discharge pressure Pd in the discharge chamber H3, and the back pressure Pm in the back-pressure chamber H4. In the first state, the switching valve 900 connects the discharge chamber H3 with the back-pressure chamber H4 in communication.

In the second state, the switching valve 900 connects the back-pressure chamber H4 with the suction chamber H1 in communication. When the scroll unit 300 is in operation, the switching valve 900 switches to the first state and permits the supply of a back pressure to the back-pressure chamber H4. When scroll unit 300 is not in operation, the switching valve 900 switches to the second state and discharges the lubricating oil present in the back-pressure chamber H4 to the suction chamber H1. This reduces an absolute amount of contamination introduced into the back-pressure control valve 860 and prevents or reduces functional disturbance of the back-pressure control valve 860.

To allow disposition of the switching valve 900 at some midpoint of the back-pressure supply passage L1, the back-pressure supply passage L1 is bent at an acute angle at a point downstream of the orifice 840, and the downstream end of the back-pressure supply passage L1 opens to the back-pressure chamber H4. As shown in FIGS. 3 to 10, a larger diameter hole 600B is formed in a portion, facing the bend of the back-pressure supply passage L1, of the outer surface of the support member 600. The larger diameter hole 600B has a diameter larger than that of the back-pressure supply passage L1 and extends to the bend of the back-pressure supply passage L1. An annular valve seat 600C is formed at the deepest portion, through which the back-pressure supply passage L1 extends, of the larger diameter hole 600B.

FIGS. 3 and 4 show a first embodiment of the switching valve 900.

The switching valve 900 is housed in the larger diameter hole 600B formed in the support member 600. Specifically, the switching valve 900 includes a holder 920, a valve member 940, a compression coil spring 960, and an O-ring 980. The holder 920 has a bottomed cylindrical shape with an opening at one end in the axial direction. The valve member 940 is disposed axially displaceably with respect to the holder 920. The compression coil spring 960 is disposed between the bottom wall of the holder 920A and the valve member 940.

The holder 920 is press-fitted and fixed into the larger diameter hole 600B so that its bottom wall partially closes the opening of the larger diameter hole 600B. A through hole 920A is formed in a center portion of the bottom wall of the holder 920, so that the discharge chamber H3 and the suction chamber H1 can communicate with each other through the through hole 920A and the back-pressure supply passage L1. The valve member 940 is a kind of so-called poppet valve, and includes a truncated conical head portion 940A and a columnar stem portion 940B disposed coaxially with the head portion 940A. The stem portion 940B of the valve member 940 is inserted into the holder 920 with an annular gap between the stem portion 940B and the inner peripheral surface of the holder 920. Being axially displaceable with respect to the holder 920, the valve member 940 is capable of coming into contact with and separating from the valve seat 600C located at the deepest portion of the larger diameter hole 600B. The compression coil spring 960 biases the valve member 940 toward the valve seat 600C. The O-ring 980 is fitted into a circumferential groove formed in the outer peripheral surface of the stem portion 940B of the valve member 940. The O-ring 980 ensures the airtightness between the inner peripheral surface of the holder 920 and the outer peripheral surface of the stem portion 940B when the switching valve 900 is switched to the first state in which the switching valve 900 connects the discharge chamber H3 with the back-pressure chamber H4 in communication.

When the scroll unit 300 is in operation, it is necessary to supply the lubricating oil separated by the oil separator 740 to the back-pressure chamber H4. Thus, when the scroll unit 300 is in operation, the valve member 940 of the switching valve 900 is moved away from the valve seat 600C of the support member 600, as shown in FIG. 3. Thereby, the switching valve 900 connects the discharge chamber H3 with the back-pressure chamber H4 in communication and blocks communication between the suction chamber H1 and the discharge chamber H3 and between the suction chamber H1 and the back-pressure chamber H4.

When the scroll unit 300 is in operation, the suction pressure Ps in the suction chamber H1, the discharge pressure Pd in the discharge chamber H3, and the back pressure Pm in the back-pressure chamber H4 satisfy the relationship: suction pressure Ps<back pressure Pm<discharge pressure Pd. In this case, the valve member 940 is biased by a valve closing biasing force of the compression coil spring 960, and pressed by a valve closing force caused by the suction pressure Ps as well as a valve opening force caused by the back pressure supplied from the orifice 840. Here, the spring coefficient and natural length of the compression coil spring 960, the suction pressure Ps applied to the valve member 940, and the pressure receiving area of the back pressure supplied from the orifice 840, etc. may be appropriately determined in consideration of the operation characteristics of the scroll compressor 100. Thus, these factors may be appropriately determined so that when the scroll unit 300 is in operation, the switching valve 900 is switched to the first state in which the switching valve 900 connects the discharge chamber H3 with the back-pressure chamber H4 in communication.

On the other hand, when the scroll unit 300 stops its operation, the lubricating oil present in the back-pressure chamber H4 is to be discharged to the suction chamber H1 so as to ensure that contamination mixed in the lubricating oil is not introduced into the back-pressure control valve 860. Thus, when the scroll unit 300 is not in operation, the valve member 940 of the switching valve 900 is in contact with the valve seat 600C of the support member 600 so as to block communication between the discharge chamber H3 and the back-pressure chamber H4 while providing communication between the back-pressure chamber H4 and the suction chamber H1, as shown in FIG. 4.

When the scroll unit 300 is not in operation, the suction pressure Ps in the suction chamber H1, the discharge pressure Pd in the discharge chamber H3, and the back pressure Pm in the back-pressure chamber H4 satisfy the relationship: back pressure Pm=discharge pressure Pd=suction pressure Ps. In this case, the forces caused by the pressures are balanced with each other, so that only the valve closing biasing force of the compression coil spring 960 acts on the valve member 940. Thus, the spring coefficient and natural length of the compression coil spring 960 may be appropriately determined in consideration of the operation characteristics of the scroll compressor 100 so that when the scroll unit 300 is not in operation, the switching valve 900 is switched to the second state in which the switching valve 900 connects the back-pressure chamber H4 with the suction chamber H1 in communication.

When the scroll unit 300 stops its operation, the contamination mixed in the lubricating oil that is present in the back-pressure chamber H4 settles as a precipitate by gravity. Thus, disposing the switching valve 900 vertically below the back-pressure chamber H4 facilitates discharging the contamination that has settled in the back-pressure chamber H4 into the suction chamber H1 together with the lubricating oil. This reduces the absolute amount of contamination remaining in the back-pressure chamber H4, and thus, for example, minimizes the probability that the contamination can be introduced into the back-pressure control valve 860 and can clog the filter contained in the back-pressure control valve 860 when the scroll unit 300 is restarted. This technical concept is also applicable to the second and third embodiments of the switching valve 900 described below.

FIGS. 5 and 6 show a second embodiment of the switching valve 900. To avoid confusion with the switching valve 900 according to the first embodiment, the reference numeral “1000” will be assigned to the switching valve of the second embodiment. In addition, in the following description for the switching valve 1000 according to the second embodiment, the same features as those of the switching valve 900 according to the first embodiment will be described briefly to avoid duplicate description. Please also refer to the description for the first embodiment, if necessary.

The switching valve 1000 is housed in the larger diameter hole 600B formed in the support member 600. Specifically, the switching valve 1000 includes a holder 1020, a valve member 1040, a compression coil spring 1060, and an O-ring 1080. The holder 1020 has a bottomed cylindrical shape with an opening at one end in the axial direction. The valve member 1040 is disposed axially displaceably with respect to the holder 1020. The compression coil spring 1060 is disposed between the bottom wall of the holder 1020 and the valve member 1040.

Unlike the first embodiment, the valve member 1040 has a stepped columnar shape with two diameters, the larger of which is closer to the valve seat 600C of the support member 600 in order, for example, to facilitate the manufacture of the valve member 1040. The valve member 1040 is adapted such that the free end surface of the larger diameter portion can come into contact with and separate from the valve seat 600C. The valve member 1040 provides operational advantages and effects similar to those described in the first embodiment. Thus, description therefor will be omitted.

FIGS. 7 and 8 show a third embodiment of the switching valve 900. To avoid confusion with the switching valves 900 and 1000 according to the first and second embodiments, the reference numeral “1100” will be assigned to the switching valve of the third embodiment. In addition, in the following description for the switching valve 1100 according to the third embodiment, the same features as those of the switching valve 900 according to the first embodiment will be described briefly to avoid duplicate description. Please also refer to the description for the first embodiment, if necessary.

The switching valve 1100 is housed in the larger diameter hole 600B formed in the support member 600. Specifically, the switching valve 1100 includes a holder 1120, a valve member 1140, a compression coil spring 1160, and an O-ring 1180. The holder 1120 has a bottomed cylindrical shape with an opening at one end in the axial direction. The valve member 1140 has a columnar shape and is disposed axially displaceably with respect to the holder 1020. The compression coil spring 1160 is disposed between the bottom wall of the holder 1120 and the valve member 1140.

When the scroll unit 300 is in operation, it is necessary to supply the lubricating oil separated by the oil separator 740 to the back-pressure chamber H4. Thus, when the scroll unit 300 is in operation, the valve member 1140 of the switching valve 1100 is moved away from the valve seat 600C of the support member 600, as shown in FIG. 7. Thereby, the switching valve 1100 connects the discharge chamber H3 with the back-pressure chamber H4 in communication and blocks communication between the suction chamber H1 and the discharge chamber H3 and between the suction chamber H1 and the back-pressure chamber H4.

When the scroll unit 300 is in operation, the suction pressure Ps in the suction chamber H1, the discharge pressure Pd in the discharge chamber H3, and the back pressure Pm in the back-pressure chamber H4 satisfy the relationship: suction pressure Ps<back pressure Pm<discharge pressure Pd. In this case, the valve member 1140 is biased by a valve closing biasing force of the compression coil spring 1160, and pressed by a valve closing force caused by the suction pressure Ps as well as a valve opening force caused by the back pressure supplied from the orifice 840. Here, the spring coefficient and natural length of the compression coil spring 1160, the suction pressure Ps applied to the valve member 1140, and the pressure receiving area of the back pressure supplied from the orifice 840, etc. may be appropriately determined in consideration of the operation characteristics of the scroll compressor 100. Thus, these factors may be appropriately determined so that when the scroll unit 300 is in operation, the switching valve 1100 is switched to the first state in which the switching valve 1100 connects the discharge chamber H3 with the back-pressure chamber H4 in communication.

On the other hand, when the scroll unit 300 stops its operation, the lubricating oil present in the back-pressure chamber H4 is to be discharged to the suction chamber H1 so as to ensure that contamination mixed in the lubricating oil is not introduced into the back-pressure valve 860. Thus, when the scroll unit 300 is not in operation, the valve member 1140 of the switching valve 1100 is in contact with the valve seat 600C of the support member 600 so as to block communication between the discharge chamber H3 and the back-pressure chamber H4 while providing communication between the back-pressure chamber H4 and the suction chamber H1, as shown in FIG. 8.

When the scroll unit 300 is not in operation, the suction pressure Ps in the suction chamber H1, the discharge pressure Pd in the discharge chamber H3, and the back pressure Pm in the back-pressure chamber H4 satisfy the relationship: back pressure Pm=discharge pressure Pd=suction pressure Ps. In this case, the forces caused by the pressures are balanced with each other, so that only the valve closing biasing force of the compression coil spring 1160 acts on the valve member 1140. Thus, the spring coefficient and natural length of the compression coil spring 1160 may be appropriately determined in consideration of the operation characteristics of the scroll compressor 100 so that when the scroll unit 300 is not in operation, the switching valve 1100 is switched to the second state in which the switching valve 1100 connects the back-pressure chamber H4 with the suction chamber H1 in communication.

In the switching valve 900 according to the first embodiment and the switching valve 1000 according to the second embodiment, recesses 940C and 1040A, each of which has, for example, a hemispherical shape, may be formed in the free end surfaces of the valve members 940 and 1040, respectively. Specifically, as shown in FIGS. 9 and 10, each of the recesses 940C and 1040A may be formed so as to extend internally from the end surface at a position facing the back-pressure supply passage L1. This allows the switching valve 900 and 1000 to receive the lubricating oil having passed through the orifice 840, and thus, to receive an increased valve opening force caused by the discharge pressure Pd.

Hereinabove, the embodiments for implementing the present invention have been described. However, the present invention is not limited to the embodiments described above, and various changes and modifications may be made based on the technical concept of the present invention as illustrated by the following examples.

The scroll compressor 100 may be configured such that an externally supplied force is used to drive the drive shaft 420. Furthermore, each of the switching valves 900, 1000, and 1100 does not have to be disposed in a portion, downstream of the orifice 840, of the back-pressure supply passage L1, and may alternatively be disposed in a portion, upstream of the orifice 840, of the back-pressure supply passage L1. Furthermore, the switching valves 900, 1000, and 1100 need not necessarily be configured to provide communication between the back-pressure chamber H4 and the suction chamber H1 when the scroll unit 300 is not in operation. Alternatively, the switching valves 900, 1000, and 1100 may be configured to provide communication between the back-pressure chamber H4 and the space H5, which is located in the outer peripheral portion of the scroll unit 300, when the scroll unit 300 is not in operation.

REFERENCE SYMBOL LIST

-   100 Scroll compressor -   300 Scroll unit -   320 Fixed scroll -   340 Orbiting scroll -   900 Switching valve -   1000 Switching valve -   1100 Switching valve -   H1 Suction chamber -   H3 Discharge chamber -   H4 Back-pressure chamber -   L1 Back-pressure supply passage (Communication passage) 

1. A scroll compressor comprising: a scroll unit having a fixed scroll and an orbiting scroll; a discharge chamber into which fluid compressed by the scroll unit is discharged; a back-pressure chamber configured to apply a back pressure that presses the orbiting scroll against the fixed scroll; and a switching valve disposed at some midpoint of a communication passage connecting the discharge chamber and the back-pressure chamber in communication, and configured to switch between a first state and a second state in accordance with an operational state of the scroll unit, wherein the switching valve connects the discharge chamber with the back-pressure chamber in communication in the first state, and the switching valve connects the back-pressure chamber with a space external to the back-pressure chamber in communication in the second state.
 2. The scroll compressor according to claim 1, wherein the switching valve switches to the first state when the scroll unit is in operation, and switches to the second state when the scroll unit is not in operation.
 3. The scroll compressor according to claim 1, wherein the space external to the back-pressure chamber is a suction chamber into which fluid is drawn from an external device.
 4. The scroll compressor according to claim 3, wherein the switching valve switches between the first state and the second state in accordance with pressures in the discharge chamber, the back-pressure chamber, and the suction chamber.
 5. The scroll compressor according to claim 1, wherein the switching valve is located vertically below the back-pressure chamber.
 6. The scroll compressor according to claim 2, wherein the space external to the back-pressure chamber is a suction chamber into which fluid is drawn from an external device.
 7. The scroll compressor according to claim 2, wherein the switching valve is located vertically below the back-pressure chamber.
 8. The scroll compressor according to claim 3, wherein the switching valve is located vertically below the back-pressure chamber.
 9. The scroll compressor according to claim 4, wherein the switching valve is located vertically below the back-pressure chamber. 